Process for the preparation of chlorophenylphosphanes

Abstract

Preparation of chlorophenylphosphanes of the formula (C.sub.6 H.sub.5).sub.n PCl.sub.3-n in which n is 1 or 2, triphenylphosphane (C 6 H 5 ) 3 P and phosphorus trichloride PCl 3 are reacted at temperatures above 300° C., for which liquid triphenylphosphane and gaseous phosphorus trichloride are introduced in a molar ratio of 1:(3 to 12) at the upper end of a vertically arranged, elongated and heated reaction zone. The reaction product discharged at the lower end of the reation zone is transferred to a residence zone charged with phosphorus pentachloride. Finally, the excess phosphorus trichloride is removed from the reaction product, via a subsequent fractionating zone, by heating the residence zone with the resultant formation of a PCl 3 -depleted reaction product. The substances contained in the PCl 3 -depleted reaction product are separated from one another by fractionated rectification under reduced pressure.

I claim: 
     
       1. A process for the preparation of chlorophenylphosphanes of the formula   (C.sub.6 H.sub.5).sub.n PCl.sub.3-n     in which n is 1 or 2, which comprises introducing liquid triphenylphosphane and gaseous phosphorus trichloride in a molar ratio of 1:(3 to 12) at the upper end of a vertically arranged, elongated reaction gone having temperatures of 350° to 650° C. in the reaction zone, transferring the reaction product discharged at the lower end of the reaction zone to a residence zone charged with phosphorus pentachloride, removing excess phosphorus trichloride from the reaction product, via a subsequent fractioning zone, by heating the residence zone with the resultant formation of a PCl 3  -depleted reaction product, and separating the substances contained in the PCl 3  -depleted reaction product by fractionated rectification under reduced pressure.   
     
     
       2. The process as claimed in claim 1, wherein the reaction zone is filled at least 50% of its length with a bulk material comprising granular silicon carbide. 
     
     
       3. The process as claimed in claim 1, wherein the silicon carbide of the bulk material has particle sizes of 2 to 8 mm. 
     
     
       4. The process as claimed in claim 1 wherein the reaction zone in the region of the silicon carbide bulk material has temperatures of 500° to 600° C. 
     
     
       5. The process as claimed in claim 1, wherein the reaction zone comprises an electrically heatable silicon/silicon carbide tube.